Microsoft Exchange Server 2013: Connectivity, Clients, and UM

CAS architecture demystified

In Exchange 2013, the CAS has evolved further into what appears on the surface to be a simple proxy that handles client connections. However, a great deal is going on below the apparently simple surface, and you explore it in this chapter. How did the CAS role reach this point? As Exchange has changed over time, Microsoft has steadily worked to separate three related parts of Exchange that began life as a set of closely coupled subsystems:

• The code that handles mailbox storage, transport, and processing. The Information Store service is the best-known part of this code, but lots of other components contribute to moving messages between sender and recipient and then storing them for future use.

• The code that handles interactions ...